The present invention relates to a well plug and method for selectively restricting fluid flow in a well. More particularly, the present invention relates to an improved apparatus and method for installing a dissolvable plug in a well and for selectively contacting the well plug with a fluid to dissolve the plug.
Well completion equipment is installed in hydrocarbon producing wells to facilitate the production of hydrocarbons from subsurface formations to the well surface. Temporary plugs are installed in the production tubing to accomplish various tasks. For example, a temporary plug can be installed in the lower end of the production tubing to permit tests for the pressure bearing integrity of the tubing. Additionally, the plug can permit the selective pressurization of the tubing to permit the operation of pressure sensitive tools within the tubing.
Temporary plugs are typically removed from the well by mechanical retrieval techniques such as wirelines, slick lines, and coiled tubing. Because other well operations cannot be performed during such work, the retrieval of the temporary plug delays the well operations and adds additional cost to the well operations.
Various techniques have been developed to reduce the time necessary to retrieve temorary well plugs. For example, one technique uses a phenolic disk packed with explosives. An electrical signal to an actuator activates the explosives and fractures the phenolic disk. This technique requires hazardous explosives and leaves phenolic fragment chunks in the well that can interfere with other well completion equipment.
Another temporary plug technique uses a glass disk to temporarily seal the well tubing. When ruptured with fluid pressure or mechanical devices, the glass fractures into small slivers to open the tubing bore. Although the glass fragments are smaller than the fragments left by a phenolic disk, the glass disks are brittle and do not reliably support large differential fluid pressures within the well. The glass disks can inadvertently rupture, leading to failure of the completion operations.
Accordingly, a need exists for a temporary well plug that does not interfere with well completion activities, that reliably seals production tubing in a well, and that does not leave plug fragments within the well or well tubing.